The concept of pre-pay billing for the provision of services is well known, particularly in the field of mobile communications. For example, wireless communication network operators implement pre-pay billing systems in which a user of the network has an associated account into which credit must be deposited prior to making use of services provided by the network. A user is typically required to have a sufficient value of credit in the associated account in order to make use of the available network service(s). Thus, if an insufficient value of credit (for example, zero) is available in the associated account, the user is unable to use the network service(s) and must increase the value of credit in the account before the service(s) can be used.
A common way to increase the value of credit in an account is to purchase a voucher in exchange for money. The voucher provides information which the user can then register with the network operator. Based on the information provided, the network operator increases the value of credit in the user's associated account. Thus, in certain situations, for example in the middle of the night, crediting an account using such a method may be inconvenient or impossible.
In certain circumstances, the value of credit in a user's account can diminish to zero whilst the service is being used, thus resulting in the user being disconnected from the network so that no further use of the service can be made (until the account has sufficient credit once again).
In an attempt to avoid a user being disconnected from a network service as soon as the user runs out of sufficient credit, it is known to grant an over-draft facility of credit, typically based on credit history or as a customer loyalty reward, so that the user can finish making use of the service at their own accord.
This is not desirable for the provider of the additional credit, since they must provide a value of credit which may not be repaid.